Swept through a time-space warp at the height of the American Civil War, Union Colonel Andrew Keane and his hard-fighting regiment found themselves stranded forever on a distant world ruled by alien creatures. After four years of fighting the Rebs, Keane's battle-hardened boys discovered that the creatures' crossbows, swords and spears were no match for union rifles. But it didn't take long for the odds to even up. The humans fought hard and bravely, and after defeating their adversaries on the land and on the sea, Keane and his troops had hoped to live in peace. But it was not to be.

Thanks to a human traitor, the aliens acquired a decisive edge - air power. And in their bloodthirsty quest for vengeance, they plotted to crush the humans once and for all - and forever reinstate their bloody reign of terror...